Incandescent lamp



NOV.-7, 1939. A, SOCOLQFSKY I 2,179,437

INCANDESCEN'I' LAMP Filed Aug. 10, 1938 INVHVTOR.

Patented Nov. 7, 1939 UNITED STATES PATENT OFFICE INCANDESCENT LAMP Arthur R. Socolofsky, Chicago, lll.

Application August 10, 1938, Serial No. 224,011 3 Claims. 01. 176-16) This invention relates to improvements in incandescent lamps and one of the objects of the invention is to providea more eificient lamp of a smaller size and one having a longer life than heretofore and to increase the lighting efiiciency thereof.

A further object is to provide an improved lamp of this character in which the heat losses therefrom will be reduced to a minimum.

A further object is to provide a lamp of this character which will provide an improved color of light, such color being more nearly white.

Other and further objects of this invention will be apparent from the following description and from the accompanying drawing of an exemplification thereof in which Figure l is a sectional view of an improved lamp of this character constructed in accordance with the principles of this invention.

Figure 2 is a view similar to Figure 1 of a modified form of the invention.

According to the present invention there is provided an outer bulb ID in which is arranged an inner bulb l l, which is considerably smaller than the outer bulb. Both of the bulbs are hermetically sealed and are out of communication with each other, the space 12 between the bulbs being evacuated.

A filament l3 of suitable material is sealed in the inner bulb H, and the usual leading in conductors M-lii are provided, the gases being confined within the inner bulb. The inner bulb H initially contains a small quantity of tungsten hexachloride and chlorine together with the usual argon nitrogen, or other vapors.

It is known that evaporation from a lamp filament is a simultaneous process of evaporation and condensation of evaporated atoms on the filament. That is, the rate of loss of weight of a filament depends upon the rate at which the evaporation exceeds the rate of condensation.

When the filament I3 becomes heated to a high degree, the tungsten hexachloride will be vaporized and there will be a decomposition thereof adjacent the filament, setting free tungsten atoms some of which will diffuse through the other gases to the filament and condense.

The pressure of the tungsten hexachloride is so adjusted that the rate of condensation on the filament just equals the rate of evaporation at a given temperature of the filament, thus permitting operation of the filament at a temperature just below its melting point, resulting in a very high efficiency and a much whiter light.

The tungsten atoms which diffuse away from l the filament will arrive at a point where the temperature is moderate, under which condition they will again combine with the chlorine set free in the previous decomposition process, and form hexachloride.

If a moderate amount of tungsten hexachloride is used in the inner bulb at about 300 C., the compound will not be deposited upon the bulb during the operation of the lamp because of the high vapor pressure at that temperature. A high bulb temperature is possible in the double bulb arrangement because of the insulating qualities of the evacuated space between the bulbs.

It can be readily seen that if the tungsten hexachloride is decomposed near the filament, some of the tungsten atoms set free will be deposited upon .the filament, thereby decreasing the rate of, or stopping the deterioration of the filament. The hexachloride at a distance away will difiuse towards the filament in an attempt to equalize the pressure.

The hexachloride thus difiusing into the space near the filament will also be decomposed, thereby maintaining a constant pressure of tungsten atoms near the filament. At the same time the chlorine which is set free near the filament will difiuse away from it until it reaches a zone in which the temperature is moderate, where it will again combine with any tungsten atoms which may be there.

If a little free chlorine is also placed in the bulb II, should the filament become smaller by decomposition, the evaporated atoms would combine with the extra chlorine and keep the tungsten atoms from depositing on the bulb and blackening it.,

This will also increase the pressure of the tungsten hexachloride and as the pressure is increased there will eventually be reached a point of equilibrium wherethe filament will not lose weight by evaporation, as any evaporation of the filament which takes place under such conditions will be replaced or neutralized by the condensation of free tungsten atoms at the same rate.

The excess chlorine will also displace the equilibrium point of the dissociation of tungsten hexachloride toward the higher temperature thereby setting the tungsten atoms free nearer the filament.

Furthermore, the excess chlorine will remove any possibility of the tungsten atoms forming the lower chlorides of tungsten which would be a disadvantage because they decompose at a lower temperature.

The pressure of argon or other inert gases in the bulb I i, with the tungsten hexachloride, will raise the bulb to considerably higher temperatures than would bepossible with the lower pressure of hexachloride and chlorine alone, and cause sharper temperature gradients, thereby maintaining the higher temperatures at which the hexachloride decomposes nearer the filament.

Furthermore, the argon reduces the rate of evaporationcduring the short interval of time after the filament has been lighted and before the hexachloride has had time to vaporize, and it will control the rate at which the tungsten atoms diifuse'away from the, filament.

Obviously the pressure of the various gases will depend upon the temperature of the, filament as well as the size of the inner bulb.

Filaments of other materials such as carbon or tantalum may be prevented from deteriorating by inserting into the bulb which contains the filament, a suitable compound of filament material having properties similar to those of the tungsten hexachloride.

In the form of the invention shown in Figur 2 there is provided an'additional filament l3a which is positioned in close proximity to, but out of electrical connection with the filament l3,

' and is composed of the same material as the amount of tungsten in the filament Ba.

A simple manner of regulating the weight of tungsten may be by the use of a filament l3aof a uniform size cut to a given length.

In carrying this invention into operation it is necessary that the chlorine and tungsten hexachloride which is employed in the lamp shall be ,free of oxygen andmoisture.

Throughout the specification and claims wherever the term gas is employed, it is to be construed broadly to include either a gas or vapor.

Furthermore the term active gases as employed by the applicant is to be construed to means a gas which during the operation of the lamp undergoes a chemical change, or is chemically active with respect to tungsten.

While the preferred forms of lamp have been herein shown and described, it is to be understood that various changes may be made in the details of construction and in the combination of the various parts within the scope of the claims without departing from the spirit of this invention.

What is claimed as new is:

1. An electric lamp containing a lighting filament of tungsten operable at incandescence, and also containing an inert gas and active gases, the active gases operating to set free the tungsten atoms, the tungsten atoms thus set free operating to compensate evaporation of the filament.

2. An electric lamp containing a filament of tungsten and also argon, tungsten hexachloride and chlorine gases, the hexachloride operating to decompose, adjacent the filament setting free tungsten atoms and chlorine atoms, some of the tungsten atoms condensing on the filament, compensating evaporation of the filament.

3. An electric lamp embodying two bulbs arranged one within the other, the space between the bulbs being evacuated, the inner bulb containing a filament of tungsten and also argon, tungsten hexachloride and chlorine gases, the hexachloride operating to decompose, adjacent the filament setting free tungsten atoms and chlorine atoms, some of the tungsten atoms condensing on the filament, compensating evaporation of the filament. I

ARTHUR R. SOCOLOFSKY. 

